1. Field of the Invention.
This invention relates in general to tape head assemblies, and more particularly to a tape head module assembly system and method.
2. Description of Related Art.
In high-speed data processing systems, magnetic recording has been employed for large storage capacity requirements. In magnetic storage systems, data is read from and written onto magnetic recording media utilizing magnetic transducers commonly referred to as magnetic heads. Data is written on the magnetic material by moving a magnetic recording head to a position over the magnetic material where the data is to be stored. The magnetic recording head then generates a magnetic field, which encodes the data into the magnetic material. Data is read from the media by similarly positioning the magnetic head and then sensing the magnetic field of the magnetic material. Read and write operations are independently synchronized with the movement of the media to insure that the data can be read from and written to the desired location on the magnetic material.
An important and continuing goal in the data storage industry is that of increasing the density of data stored on a medium. For tape storage systems, that goal has lead to increasing the track density on recording tape, and decreasing the thickness of the magnetic tape medium. However, the development of small footprint, higher performance tape drive systems has created various problems in the design of a tape head assembly for use in such systems.
In a tape drive system, magnetic tape is moved over the tape surface of the tape head at high speed. This movement generally entrains a film of air between the head and tape. Usually the tape head is designed to minimize the spacing between the head and the tape.
During operation, an actuator mechanism moves the head and magnetic transducers to a desired position on the surface of the moving medium where the head electromagnetically reads or writes data. Typically, the magnetic transducers are integrally fabricated in a carrier or support referred to as a “slider”. The slider generally serves to mechanically support the head transducers and any electrical connections between the head and the remainder of the storage system.
In order to meet the demand for increasing areal densities in magnetic tape, many technological innovations are required. In order to improve data reliability, a read element corresponding to each write element reads the magnetic field from the tape immediately after it is written. This technique is known as read-while-write. To increase data transfer, the tape may be written as it travels in either direction across the tape head. This requires a read element downstream of each write resulting in a read-write-read head configuration.
A read-while-write head assembly comprises a write element in-line with a read element, the gap of the read element being accurately spaced to the gap of the write element, with the read element positioned downstream of the write element in the direction of tape motion. By continually reading “just recorded” data, the quality of the recorded data is immediately determinable at a time when the original data is still available in temporary storage in the recording system. The reproduced data is checked against the original data, and appropriate action, such as re-recording, may be taken in case of error.
Conventional thin film tape heads are fabricated using processes similar to those used in DASD heads. The process provides a plurality of layers deposited on the surface of a substrate to form the tape head transducers. For a tape head assembly, the read-after-write pair of magnetic recording heads include a first write element adjacent to a read element which is adjacent to a second write element, or a first read element adjacent to a write element which is adjacent to a second read element. Cables are then electrically attached to the heads to provide signal leads.
The next step is to join the cabled heads together to form the read-while-write unit. However, the two tape head sections may shift relative to one another during this joining process. Shifting of the two modules can affect tape wrap angle, track-to-track registration, and head-to-head parallelism. Previous two module tape head build methods do not have generally the required level of precision for modern high density recording applications. Flat heads require an internal tape wrap of approximately 1.8 degrees per side.
In addition, heads are now built with flat rather than curved tape bearing surfaces, as described in U.S. Pat. No. 5,905,613. These heads, when constructed for high density recording, have critical module-to-module alignment tolerances, and required a new design and a new assembly method for controlling their tolerances.
However, in general it is very difficult to hold, align and join the two modules to one another. Moreover, the alignment precision required makes the task even more difficult, if not impossible. This problem has been addressed for cylindrically contoured tape heads, but not for the flat contoured heads. Cylindrical contoured heads rely on datum unit alignment for setting the wrap angle, and this is generally not applicable to flat contoured heads. In addition spring loaded pin tooling used for cylindrically contoured heads does not meet the increasing demands of tighter track-to-track and other alignments required by narrow track width heads because such designs are plagued by stiction and erratic setup performance, and furthermore do not provide means for gripping the modules for accurate alignment independent of other tolerances.
It can be seen then that there is a need for a tape head module assembly system and method that systematizes the holding, aligning and joining of the two modules to one another, while providing micron level alignment tolerances.